We will conduct an observational longitudinal prospective study in 3 hospitals in units with high prevalence of resistant organisms. Consenting patients will be screened for carriage of AMR organisms at admission, and those found to be carriers of the target ARB will be included in the longitudinal study. To improve the yield of screening we may use risk stratification based on risk factors identified at each center. Patients included in the longitudinal study will be asked to provide serial stool samples every 2-3 days during hospitalisation (rectal swab will be allowed as replacement for stool specimen, after developing appropriate methodology to correlate between stool samples and rectal swabs).